The present invention relates to a water pump for circulating a coolant of an internal combustion engine.
In Japanese Patent Laid-Open No. 262096/1992, there is disclosed a water pump in which a support portion in a cylindrical shape surrounding a rotating shaft is provided at a pump case, an outer end of the rotating shaft projected outwardly from the support portion is integrally coupled with a pulley formed in a cylindrical shape surrounding the support portion, a bearing is interposed between an inner face of the pulley and an outer face of the support portion and only a seal member arranged concentrically with the bearing is interposed between an inner face of the support portion and the rotating shaft.
As shown by FIG. 12, the water pump disclosed in Japanese Patent Laid-Open No. 262096/1992, is provided with the support portion or a body 2A fixed to an attaching face of a cylinder block of an internal combustion engine, a pulley portion 40A rotated by a transmission member, a shaft portion 50A in a solid shape coaxially connected to a central region of the pulley portion 40A, a bearing 6A provided between the body 2A and the pulley portion 40A for making the pulley portion 40A rotatable relative to the body 2A and a rotating blade member 8A fitted and fixed to the shaft portion 50A. When a crankshaft of the internal combustion engine is driven, a belt 49A constituting the transmission member hung at the crankshaft and the pulley portion 40A is operated to circulate to thereby rotate the pulley portion 40A. When the pulley portion 40A is rotated, the shaft portion 50A connected to the pulley portion 40A is rotated in the same direction and the rotating blade member 8A is rotated in a pump chamber of the internal combustion engine. As a result, pumping operation is achieved.
Further, according to Japanese Patent Laid-Open No. 149822/1990, there is disclosed a water pump in which a pulley is arranged surrounding a bearing support portion of a pump housing, a drain hole is formed at a lower portion of a buffer chamber formed between a seal member arranging portion and a bearing arranging portion of the bearing support portion, the drain hole is opened to an inner face of the pulley and a water storing portion is formed at the inner face of the pulley.
Meanwhile, according to the conventional water pumps, when a coolant leaked from a shaft sealing member (mechanical seal) invades the bearing, this causes a drawback in which the bearing is corroded, the sliding resistance increases or the bearing is destroyed.
Therefore, according to the conventional water pumps, in order to prevent the coolant leaked from the shaft sealing member from invading the bearing, a plurality of seal members are interposed between an inner face of a support portion of the housing and the rotating shaft other than the shaft sealing member. However, although according to such a construction, the coolant can be prevented from invading the bearing, this poses a problem in that the number of parts attached to the housing increases, shapes or fabrication of the parts becomes complicated and cost of the parts increases since both the shaft sealing member and the other seal members are all needed.
Further, according to the water pump shown in FIG. 12, the shaft portion in the solid shape projected to the side of the pump chamber and the pulley portion are separate from each other; when the water pump is integrated, the pulley portion and the shaft portion in the solid shape are successively connected and, therefore, aspects of lightweight formation and integration performance are not necessarily satisfactory.
In addition thereto, in a water pump according to the conventional technology (for example, Japanese Patent Laid-Open No. 149822/1990), a liquid leaked from the water storing portion formed at the inner face of the pulley reaches a belt engaging face of the pulley by way of an outer peripheral face of the pulley. As is well known to one skilled in the art, the transmission of rotational force by the pulley is carried out by rotating the shaft via friction force operated between the belt and the pulley by the belt constituting rotational force transmitting means. Therefore, when the liquid adheres to the belt engaging face of the pulley, there is concern for reducing the friction force and causing a loss in transmitting the rotational force. Further, the belt is generally constructed by rubber and, therefore, this poses a problem in that the belt is swollen by the adhering of the liquid, and thus its strength decreases.
Therefore, it is a technical problem of the invention to provide a water pump capable of preventing coolant leaked from a shaft sealing member from invading a bearing by a small-sized, light-weight and simple construction.
Further, it is a technical problem of the invention to be resolved, in addition to the above-described problem, to provide a water pump capable of ensuring drawability of a shaft portion integrally formed with a pulley portion of a pulley member and advantageous in shortening a length of the shaft portion.
Further, it is a technical problem of the invention to provide a water pump capable of preventing a liquid leaked from a shaft sealing member from reaching a belt engaging face by a small-sized, light-weight and simple construction.
According to an aspect of the invention, the above-described problems are resolved by providing a water pump comprising:
a pulley rotated by receiving a torque from a drive source, and having a shaft portion which is integrally formed therewith and extended in a shaft core direction at a central portion thereof;
an impeller fixed to the shaft portion and rotated integrally with the shaft portion;
a body forming a water chamber arranged with the impeller;
a cylindrical portion provided by projecting from the body in a cylindrical shape;
a bearing rotatably supporting the pulley at the cylindrical portion; and
a shaft sealing member for sealing the bearing against the water chamber;
wherein the shaft sealing member is attached to either one of an inner peripheral face and an outer peripheral face of the cylindrical portion.
Preferably, the shaft portion includes a hollow chamber, the impeller includes a central boss portion and blades, and the central boss portion is fitted to an inner portion of the shaft hollow chamber of the shaft portion.
An outer ring of the bearing is attached to an inner peripheral face of the pulley, an inner ring thereof is attached to an outer peripheral face of the cylindrical portion and the shaft sealing member is attached to an inner peripheral face of the cylindrical portion and the pulley is provided with a projected portion projected to an outer side in a diameter direction in a space between the shaft sealing member of the pulley and the bearing.
According to a preferred example of the invention, the inner ring of the bearing is attached to the outer peripheral face of the cylindrical portion formed at the body and the shaft sealing member is attached to the inner peripheral face of the cylindrical portion and, therefore, at least portions of the shaft sealing member and the bearing in the axial direction, which have conventionally been arranged at positions extended in the axial direction, can be arranged to overlap, and the length of the shaft portion of the water pump in the axial direction can be shortened. Therefore, the water pump can be downsized and its mountability can be promoted.
The pulley member used in the invention is provided with a pulley portion rotated by a wrapping transmission member such as a belt and the shaft portion integral with the pulley portion. The shaft portion is provided at a central region of the pulley portion by squeeze-drawing substantially coaxially therewith. The shaft portion is constructed by a cylindrical shape penetrated in the axial length direction and is provided with the shaft hollow chamber extended in the axial length direction, a front end opening disposed on a front end side of the shaft hollow chamber, and a base end opening disposed on a base end side of the shaft hollow chamber. In this way, the shaft portion is constructed by the cylindrical shape extending in the axial length direction and is constructed by an unbottomed hollow shape which is not provided with a bottom wall portion. Therefore, in comparison with a case of a bottomed hollow portion having the bottom wall portion, the squeeze-drawability of a peripheral wall of the shaft portion is ensured.
Further, a central boss portion of a rotating blade member is fitted to an inner portion of the shaft hollow chamber of the shaft portion of the pulley member. Therefore, in comparison with the case in which the central boss portion of the rotating blade member is fitted to an outer portion of the shaft portion of the pulley member, a projecting degree of projecting a front end portion in the axial length direction of the shaft portion to a side of the rotating blade member is reduced. The above-described construction is thus advantageous in shortening the formation of the axial length of the shaft portion and also in this regard, the squeeze-drawability of the shaft portion is ensured.
Further, according to a preferable example of the invention, a liquid leaked from the shaft sealing member is dropped at a portion provided at the pulley and projected to an outer side in the diameter direction. A water cutting effect is thus achieved and the liquid can be prevented from adhering to the belt by the flowing of the liquid to the belt engaging face of the pulley engaged with the belt.
The projected portion of the pulley can store a predetermined amount or volume of the liquid. At this occasion, the level of the stored liquid can always be made lower than the inner peripheral face of the belt engaging face by adjusting means. Therefore, the stored liquid can be prevented from invading the inner peripheral face of the belt engaging face.